Costa Rica

Central Valley Region

The Central Valley Weather Region includes parts of the provinces of Heredia, San Jose, Alajuela and Cartago, including popular cites like San Jose, Heredia, Escazu, Santa Ana, Cartago, Barva and Grecia, among many others. 

The average annual temperatures range from 72°F and 75°F, and these do not vary much throughout the year. The max usually averages 84°F and the lowest averages 64°F. Relative humidity averages about 75%, dropping to 69% during the dry season. 

The dry season is December to March, with April and November being months of transition. July tends to be the driest of the wet months and is considered a little dry season. During the dry season, the humidity is lower. The months of January through March are also marked with persistent northeast winds and lots of sun. 

The rainy season months of May through November are characterized by less sun and more rain.  Usually, you get at least four hours of sun in the morning before the afternoon storms develop. September and October are the rainiest months (averaging 26 inches per month) of the year, and the most humid. The Central Valley region receives 77.4 inches of rain annually. 

As you ascend into the mountains north of Heredia, especially up past Barva, the weather tends to be cooler and cloudier.

Alajuela

Month	Average Highs		Average Lows		Average Rainfall		Humidity
	F	C	F	C	in.	mm	%
Jan.	81	27	62	17	0.28	7	69
Feb.	83	28	62	17	0.47	12	69
Mar.	85	29	63	17	0.55	14	67
Apr.	85	29	63	17	3.23	82	70
May	82	28	64	18	10.67	271	82
Jun.	81	27	64	18	10.63	270	82
Jul.	81	27	64	18	7.09	180	84
Aug.	81	27	63	17	10.16	258	79
Sep.	80	27	63	17	13.7	348	82
Oct.	80	27	63	17	13.39	340	87
Nov.	80	27	63	17	19.57	497	86
Dec.	81	27	63	17	20.87	530	80

Cartago

Month	Average Highs		Average Lows		Average Rainfall		Humidity
	F	C	F	C	in.	mm	%
Jan.	73	23	55	13	1.2	31	78
Feb.	74	23	54	12	0.73	19	79
Mar.	77	25	55	13	0.6	16	77
Apr.	78	26	56	13	1.85	48	79
May	79	26	58	14	7.27	187	83
Jun.	77	25	57	14	7.87	202	83
Jul.	77	25	58	14	5.06	130	83
Aug.	77	25	57	14	6.06	156	84
Sep.	77	25	56	14	9.71	249	84
Oct.	78	25	57	14	9.78	251	85
Nov.	75	24	57	14	4.31	110	84
Dec.	73	23	56	14	2.28	58	8

Grecia

Month	Average Highs		Average Lows		Average Rainfall		Humidity
	F	C	F	C	in.	mm	%
Jan.	84	29	63	17	0.29	7	70
Feb.	86	30	64	18	0.48	12	69
Mar.	87	31	65	18	0.58	15	68
Apr.	87	31	65	18	2.7	69	71
May	84	29	65	19	10.07	258	83
Jun.	82	28	65	18	10.83	278	87
Jul.	82	28	65	18	7.56	194	83
Aug.	82	28	64	18	10.49	269	85
Sep.	81	27	64	18	13.12	336	89
Oct.	81	27	64	18	12.79	328	89
Nov.	82	28	64	18	5.69	146	84
Dec.	83	28	64	18	1.23	32	74

Heredia

Month	Average Highs		Average Lows		Average Rainfall		Humidity
	F	C	F	C	in.	mm	%
Jan.	76	24	59	15	0.78	20	73
Feb.	75	24	57	14	0.96	25	72
Mar.	79	26	58	15	1.91	49	71
Apr.	79	26	59	15	4.86	125	74
May	78	26	61	16	12.49	320	83
Jun.	76	25	59	15	12.88	330	85
Jul.	76	25	60	16	8.03	205	82
Aug.	76	25	60	16	9.73	249	84
Sep.	76	24	59	15	15.55	399	87
Oct.	76	25	59	15	16.42	421	87
Nov.	75	24	60	15	7.02	180	82
Dec.	75	24	60	16	2.14	55	76

Irazu Volcano

Month	Average Highs		Average Lows		Average Rainfall		Humidity
	F	C	F	C	in.	mm	%
Jan.	52	11	39	4	1.34	34	80
Feb.	52	11	39	4	2.36	60	76
Mar.	64	18	40	4	1.1	28	74
Apr.	54	12	40	4	3.86	98	81
May	53	12	41	5	8.27	210	87
Jun.	51	11	42	6	8.9	226	91
Jul.	50	10	41	5	6.77	172	90
Aug.	51	11	39	4	8.27	210	90
Sep.	51	11	41	5	8.94	227	90
Oct.	51	11	41	5	10.63	270	90
Nov.	61	16	41	5	11.42	290	89
Dec.	51	11	39	4	6.38	162	83

Poas Volcano

Month	Average Highs		Average Lows		Average Rainfall		Humidity
	F	C	F	C	in.	mm	%
Jan.	69	21	53	12	5.91	150	82
Feb.	89	32	53	12	3.82	97	81
Mar.	71	22	53	12	1.65	42	82
Apr.	71	22	55	13	4.8	122	83
May	71	22	57	14	13.7	348	90
Jun.	71	22	57	14	16.54	420	91
Jul.	69	21	57	14	14.13	359	89
Aug.	69	21	57	14	18.03	458	89
Sep.	71	22	55	13	19.41	493	91
Oct.	59	15	57	14	16.77	426	91
Nov.	58	14	57	14	16.89	429	89
Dec.	59	15	57	14	12.99	330	85

San Jose

Month	Average Highs		Average Lows		Average Rainfall		Humidity
	F	C	F	C	in.	mm	%
Jan.	73	23	59	15	0.39	10	82
Feb.	75	24	59	15	0.24	6	80
Mar.	77	25	60	16	0.47	12	78
Apr.	78	26	60	16	1.73	44	79
May	78	26	62	17	8.86	225	84
Jun.	78	26	62	17	11.3	287	85
Jul.	77	25	62	17	8.46	215	84
Aug.	77	25	62	17	9.8	249	85
Sep.	76	24	60	16	13.07	332	86
Oct.	77	25	60	16	13.07	332	86
Nov.	75	24	60	16	5.59	142	84
Dec.	73	23	59	15	1.61	41	83

Source: National Weather Services of Costa Rica