WEATHER IN MEXICO
Mexico is a large country and much of the interior is above one mile in elevation. The Northern border with the USA is home to one of the driest deserts on Earth (the Sonora Desert) while the Southern border cuts across one of the last remaining virgin rain forests in the Western Hemisphere (The El Peten). Mexico is definitely an "East - West" country as well. Tijuana and Ensenada are due South of San Diego while the resort city of Cancun is almost due South of Pensacola Florida. Several major weather system components are involved in the country's normal weather "makeup" and it would be a mistake to believe (as the travel brochures suggest) that "The weather south of the border is always topical balmy". Except for the Northern Baja California peninsula, and Northwestern Sonora and Chihuahua, summer is the rainy season in Mexico and the month of May is generally regarded as the hottest month throughout the country ! except Baja and the mainland Pacific Coast.
The further south you go, the warmer and more humid it will be, and the higher you go the cooler and drier it will be. But that's where the generalities end.
Winter weather fronts sweep down from the USA and impact Mexico's weather as far south as Manzanillo on the West Coast (About half the distance to Guatemala) and Cancun on the East Coast. Summertime Caribbean hurricanes can impact the entire East coast from June to mid-November. Tehuantepec (Pacific) hurricanes can strike from Manzanillo to Mazatlan (including the Baja peninsula to around Loreto, two-thirds the down the length of the peninsula). The general direction of travel of Eastern hurricanes is West and North, and the same holds true for Pacific "Chubascos" (as hurricanes are called in Baja).
It would be most convenient and relevant to focus on popular RV destinations rather than each and every area of the country. Below you will find the following areas with descriptions: Baja California, Pacific Coast, Yucatan, Colonial Cities, and Copper Canyon. Bear in mind that micro-climates in each region can vary the weather appreciably.
Note: Think of "Climate" as what the book says things should be like and of "Weather" as the stuff that actually blows in (and out).
The eight hundred mile long peninsula has four primary influences upon it: The cool Pacific ocean tempers the climate on Baja's West coast, while the sheltered Gulf of California (Sea of Cortez) influences the Eastern half (A spine of mountains divides the halves). The third influence is wintertime cold fronts sweeping down from the Northern Pacific that can affect weather all the way to Cabo. In the summer months impulses of very warm moist air (along with the prevailing winds) arrive from the south and east.
A typical February day at Concepcion Bay (an RV'ers Mecca near the village of Mulege) will see a daytime temperature near seventy, an overnight low in the high forties, low fifties and humidity around thirty five percent. In August however, beach temperatures can soar to a hundred and ten, with seventy percent humidity. Most people find the average winter daytime temperature a bit too cool for shorts and tee shirts. The weather really starts to get consistently balmy in April and by May it is just about perfect. By contrast it is almost always too cool for shorts year-round from the border to Guerrero Negro (Baja's Pacific side)
The main weather detraction in the Winter are windy periods that bring chilly fifty degree temperatures from out of the North and foaming whitecaps to an otherwise placid gulf. The winds can last anywhere from two days to two weeks and they can shriek to forty miles per hour raising clouds of dust. In between the periods of wind are the balmy seventy five degree days that everyone prefers to remember.
Summer hurricanes are limited in their Northward adventures because of cool ocean water from Guerrero Negro (which is located halfway down the peninsula) North. They either turn hard west, or hard east at this point or risk having the life sucked out of them by sixty degree water. Cabo San Lucas is struck by a hurricane less than once every seven summers. A few summers ago I recorded daily "low" temperatures in the range of eighty-seven degrees (with ninety percent humidity) in Mulege. That occurred just at dawn!
It is interesting to note while on the road, a definite increase in the humidity as you descend from the Central ridge of mountains down to the shores of the gulf. The humidity increase is present summer and winter. As a matter of fact the Pacific ocean influences the climate to the point of an eighty mile distance separating Guerrero Negro from Santa Rosalia can mean a thirty degree difference in temperature! As compared to Santa Rosalia, Mulege and Loreto, Guerrero Negro is too cool for comfort in the Winter but just right in the Summer.
From La Paz to Cabo the temperatures are generally five degrees warmer than at Concepcion Bay, summer and winter. La Paz is also affected by the pesky North winds in the winter. However summertime highs in La Paz can reach a cruel one hundred fifteen degrees. Cabo San Lucas is somewhat sheltered from winter wind by a range of mountains to the North. Some travel writers boast that Cabo's summertime temperatures seldom are a hundred degrees. I must agree (wink wink) -- Because whenever the temperature climbed to a hundred it always shot past to around 102 to 104 (primarily in July). Humidity levels soar from late July to mid October, while temperatures "dip" to the high nineties. Interestingly enough, you will wake up on an unspecified morning in October and the humidity will have vanished overnight. Winter time on the Cape is the best season with an average daytime temp in the low eighties. Hot days and chilly (62 F! ) evenings prevail in mid-June. Winter weather is mild enough for shorts and tee shirts on the cape. La Paz is borderline, with most winter evenings there too cool for summer apparel. The cooling influence of the Pacific Ocean is especially made evident in the Summer. While San Jose del Cabo may be baking at one hundred six degrees, Cabo will be simmering at a hundred and two while twenty miles North of Cabo the beach temperature will be in the low nineties.
Mexico's west coast is "shaded" by the Baja peninsula from the border with the USA all the way to Mazatlan. As such, a "Baja like" climate can be expected except there is no Pacific ocean to influence things. Below Mazatlan, a more tropical clime is encountered. The further south that you travel from this point the higher average temperature Winter temperature you're likely to encounter (From the border to Mazatlan, summer temperatures are similar to those in Concepcion Bay and La Paz). Winter winds affect boating in the Gulf but impacts things to a lesser extent than Baja on shore. Occasional winter frosts can occur as far south as Culiacan.
A typical winter day in Kino Bay or San Carlos will see temperatures in the high sixties with thirty percent humidity. Occasional breezy cold snaps will restrict daytime highs to the fifties and overnight lows can dip to the high twenties. Most winter nights remain in the upper forties to around fifty. December is the coolest month in the region, followed by January and February. Summertime high temps can reach a hundred ten, humidity can soar to eighty percent and only the promise of a (not infrequent) thunderstorm will bring some relief.
Mazatlan's temperatures are around five degrees warmer than San Carlos temperatures in the winter and ten degrees cooler in the summer months. Because Mazatlan's latitude is similar to that of La Paz, there is a threat of a very infrequent summer hurricane. From here southward for eight hundred miles, hurricanes can impact the coast (in season of course). If you are looking for really balmy winter beach weather, Mazatlan might be a tad too cool, evenings and mornings, from December until March.
Bear in mind that we are discussing the climate at the sea shore (where most folks want to camp). Just a short walk through the coconut grove can result in a temperature increase of five degrees, and a cutoff from a stiff onshore breeze.
Puerto Vallarta is definitely balmier than Mazatlan, yet brisk offshore breezes can sometimes make winter mornings (and evenings) chilly for shorts and tee shirt lovers. Most days approach eighty degrees Dec - April while nights can occasionally sag into the forties which will surprise most newcomers. Most of the time though an overnight low of mid fifties to low sixties can be expected. As such I have relegated Puerto Vallarta (and indeed the entire coastline from here south to Guatemala) as a "Year Round Shorts & Tee Shirt Haven". While "P.V." may have warmer winters it also has hot and humid summers that generally stick in the high nineties with eighty percent humidity. The best months for south-seas weather is November and March, but most people rave about everything in between as well. Bear in mind that a large majority of hurricanes that impact Mexico's west coast do so from Acapulco North to Manzanillo.
Acapulco may well be the shorts and tee shirt capital of Mexico as far as winter weather is concerned. When Guaymas, and Mazatlan are shivering under the effects of a remnant of cold front from North Dakota, Acapulco is almost always near ninety in the daytime and at "worst" low seventies at night. The "best" weather is arguably in December, January and February because that's when the ever-present humidity is at it's lowest level. Few Americans or Canadians will be around May through October though because of rain, humidity, and scorching temperatures.
Most visitors are surprised when they learn that the Yucatan peninsula cannot be referred to as "Southern Mexico". As a matter of fact if you draw a line westward it'll end up on the coast somewhere around Manzanillo which by all accounts in but halfway down Mexico's Pacific coast. This fact should give you a clue about what to expect. The second aspect of the climate is that it is heavily influenced by East Coast USA weather in the Winter and by weather traveling West across the Atlantic Ocean from Africa in the summer months.
Like Mexico's Pacific Coast, location is everything. Just a short distance inland from the beach temperatures can be as much as ten degrees warmer in the Winter and Summer.
The Caribbean coast is a major target of many visiting RV'ers. Also visiting interior ruins such as Chichen Itza are major destination objectives. Below is an example of what to expect at each:
Cancun enjoys mostly clear winter weather (as does much of the country). Temperatures on the beach range in the seventies and eighties but frequent blasts of clouds, wind and occasional light rain may sag down from the USA. Fly in tourists who have but three days to "enjoy" the resultant fifty-five degree temperature can get grumpy! Cancun's humidity is also ten to fifteen points higher as compared to Mexico's west coast resorts. Curiously enough an otherwise balmy seeming water side temperature of mid seventies seems almost clammy when combined with seventy percent humidity and a stiff breeze. For the most part however the Caribbean region offers good weather for daytime and evening beach apparel.
Interior Yucatan is a bit more schizoid as far as weather variables are concerned. I've shivered at noon in January in the shade of the great pyramid at Chichen Itza one year and panted with near heat exhaustion the next. On average however expect temps to range from the low seventies to near ninety. From May to November, temperatures can rise to one hundred twenty or more, which may be one reason why the ancient Maya sacrificed so many victims in the summer months!
The summer months from May to November are hurricane season in Yucatan and it will pay to keep a weather eye on forecasts.
The first thing to keep in mind is that all of Mexico's colonial cities are above one mile in elevation. Expect cooler temperatures summer and winter as compared to the coast. Cooler doesn't necessarily mean cold however at least in the daytime. But for the most part winter days are a bit chilly for shorts and tee shirts. The higher the city is the cooler it will be. Winter nights can be shockingly cold with frequent overnight hard freezes and a frosty windshield in the morning. While snow isn't frequent, you will welcome the use of your space heater until mid-morning. Expect daytime temperatures from the mid-fifties to low seventies, and overnight temperatures in the high thirties and forties with occasional snaps down into the teens.
The elevation which makes for cool to mild winter temperatures, also provides for a cooler and drier climate in the summer when most people flee the beaches because of heat and humidity. Rising most air as a matter of fact condenses as it reaches the cooler air aloft and East coast mountain ranges are sometimes innundated with overnight rainfall measured in feet. Most RV'ers find a summer haven in the interior where the average humidity is half that at the beach and overnight temperatures range thirty or more degrees cooler. Summer in the interior is the season for shorts and Tee shirts.
THE COPPER CANYON
For centuries the indigenous Tarahumara Indians migrated vertically within the five major canyons in the region. They journeyed up in the summer and down in the winter. This is a good point to keep in mind when occasional winter snowdrifts start to accumulate on the canyon rim. The summer sun can turn the depths of the canyon into a solar reflective oven. Winter clothing for the canyon rim should emphasize long sleeves, long pants, and a heavy coat and hat just in case. At the bottom, discreetly away from civilization one can don skimpy swim wear and submerge in the tepid Batopilas River.
Normal rim temperatures are in the fifties during the day into the teens at night during the winter, and low eighties to ninety in the summer. At the bottom, expect temps to range from the sixties to near eighty on a typical winter day and up to a hundred fifteen or more during the summer afternoon. The massive granite canyon walls act as a heat retainer and nighttime temperatures sometimes only drop three to five degrees under the daytime high.
Because the Copper Canyon is located well within the North West region of Mexico it is heavily influenced summer and winter by USA weather. As such roads and highways can be washed out by winter storms and summer thunderstorms.
More and more RV'ers are spending most of the year in Mexico. Many migrate with the seasons and as such have decided upon two places to "hang out". Here are some of the more popular choices:
Lake Chapala (near Guadalajara) from May through October, and the region around Puerto Vallarta in the remainder of the year.
The Caribbean beaches from November to April and San Cristobal de Las Casas for the summer.
Puerto Escondido in the Winter and Oaxaca in the summer.
The vast metropolis dwells in the bottom of a geographical bowl. Temperature inversions from November to March can trap obnoxious quantities of smog and pollution. But in the summer, rain showers and a persistent easterly breeze keeps the capitol's air surprisingly fresh. Like most everywhere else in Mexico May is the warmest month here. Expect hazy seventy degree January days with forty degree nights. Summer temps are usually in the seventies and eighties with nights dropping into the fifties.
As one pale skin RV'er quipped as he stood stoically in the wake of a fifty five degree Baja breeze "Anywhere in Mexico is better than back home" (Duluth Minnesota in February).
Another time I was sitting in a restaurant in the direct path of a large fan when a fresh and crisp looking lady dressed in tennis whites looked at me then raised her eyebrows: "Hell honey" she drawled "If y'all think this is hot, why don't you come to Heewston?"
Nothing separates and individualizes RV'ers like their particular intolerance to heat and cold . Canadians and other folk from the Pacific Northwest tend to flee Baja beaches when the temperature reaches ninety -- soon after their departure, other RV'ers with the constitution of an armadillo arrive from Arizona and Texas and declare the weather as "A bit on the cool side but it'll do!"
I try to take variables in Mexican weather with a large grain of salt. Earlier this year in a hotel at a favorite beach village I found myself closing the windows against a chilly February breeze and robbing the blanket off of the second bed. Just a year earlier in the same hotel during the same month, I went to sleep regularly under a whirling ceiling fan with the covers thrown back.
If I had to pin down the one RV climate accessory that I couldn't do without (besides a heater and air conditioning), it would be one (actually a pair) of those twelve volt ceiling vent fans. I do much of my camping where there are no hookups and while I find that I can always slip on a heavy shirt and long pants to ward off a chill, I have just so many layers of clothing to shed when the thermometer goes the other way. Shade can be at a premium anywhere in Mexico and rather than run a generator and the air conditioner, I can set one fan to exhaust excess heat while the one over my bed admits a fresh evening breeze.
And if I had to identify a favorite single article of optional Winter clothing (besides a hat which is mandatory for shade), it would have to be a heavy wool sweater. For some reason wool keeps me warmer in a humid or clammy environment which is common through much of Mexico in the Winter months during early morning hours. A goose down vest is nice for exploring colonial cities on a chilly winter's eve but down is almost useless when the humidity is soaring.
THE RAINY SEASON
Except for Northwestern Mexico, Winter is the dry season and July through September is when most of the rainfall occurs. Winter is never completely dry anywhere and frequent dry spells interrupt otherwise predictable afternoon summer showers.
A typical summer day starts out clear as a bell, by noon clouds start to build with showers occurring until around six. Other times it may start to rain around sunset then continue until midnight.
The main thing to remember is that it is never "constantly rainy" in Mexico. Summer thunderstorm cloudbursts can dump biblical quantities of water in a few short minutes while summer hurricanes inundate large regions with literally feet of rainfall but these events are not the norm. I would rather do without the lightning but a summer thunderstorm can suck down vast quantities of cold air from the upper atmosphere and leave me shivering in delight during a too brief respite from steamy summertime beach temperatures.
WEATHER FORECASTS ON THE WEB
Over the years I have formed two opinions about Mexico weather forecasts on the World Wide Web:
I believe but do not stake my life on forecasts and projections about an impending hurricane or other severe weather.
Local forecasts are sometimes wishful thinking, and even "current conditions" can be far off the mark. I refer to these services as "Generally Speaking".